EP0171529A2 - Circuit résonateur accordable pour un démodulateur FM à boucle d'asservissement de phase - Google Patents

Circuit résonateur accordable pour un démodulateur FM à boucle d'asservissement de phase Download PDF

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Publication number
EP0171529A2
EP0171529A2 EP85106766A EP85106766A EP0171529A2 EP 0171529 A2 EP0171529 A2 EP 0171529A2 EP 85106766 A EP85106766 A EP 85106766A EP 85106766 A EP85106766 A EP 85106766A EP 0171529 A2 EP0171529 A2 EP 0171529A2
Authority
EP
European Patent Office
Prior art keywords
circuit according
resonance circuit
inductor
inductance
center point
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP85106766A
Other languages
German (de)
English (en)
Other versions
EP0171529A3 (fr
Inventor
Michael Dipl.-Ing. Ohler
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Blaupunkt Werke GmbH
Original Assignee
Blaupunkt Werke GmbH
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Blaupunkt Werke GmbH filed Critical Blaupunkt Werke GmbH
Publication of EP0171529A2 publication Critical patent/EP0171529A2/fr
Publication of EP0171529A3 publication Critical patent/EP0171529A3/fr
Withdrawn legal-status Critical Current

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    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03D—DEMODULATION OR TRANSFERENCE OF MODULATION FROM ONE CARRIER TO ANOTHER
    • H03D3/00—Demodulation of angle-, frequency- or phase- modulated oscillations
    • H03D3/02—Demodulation of angle-, frequency- or phase- modulated oscillations by detecting phase difference between two signals obtained from input signal
    • H03D3/24—Modifications of demodulators to reject or remove amplitude variations by means of locked-in oscillator circuits
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03J—TUNING RESONANT CIRCUITS; SELECTING RESONANT CIRCUITS
    • H03J3/00—Continuous tuning
    • H03J3/02—Details
    • H03J3/16—Tuning without displacement of reactive element, e.g. by varying permeability
    • H03J3/18—Tuning without displacement of reactive element, e.g. by varying permeability by discharge tube or semiconductor device simulating variable reactance
    • H03J3/185—Tuning without displacement of reactive element, e.g. by varying permeability by discharge tube or semiconductor device simulating variable reactance with varactors, i.e. voltage variable reactive diodes

Definitions

  • the invention relates to a tunable resonant circuit for a PLL-FM demodulator for receiving satellite programs, in particular satellite television programs, with two series-connected tuning diodes, the facing electrodes of which are connected to a PLL control loop via a center point.
  • Satellite television in particular is becoming increasingly important, and it can be assumed that with the possibility of increasing - also private - providers of television programs and the possibility of feeding into cable networks, there is a growing need for corresponding circuits.
  • the linearity of the tuning characteristic of the PLL-FM demodulator is a decisive and important criterion on the receiving side in order to ensure perfect demodulation. If the tuning characteristic curve of the associated resonance circuit is unduly curved, incorrect demodulation results, with the result that the image content on the screen of a connected television set is disturbed both in terms of brightness and in terms of color reproduction. In addition, intermodulation disturbances occur in the presence of sound carriers. In principle, there is no difficulty in designing the tuning characteristic to be largely linear in the desired manner, but this is associated with a considerable additional outlay with regard to the circuit measures.
  • satellite television has so far been used only used by a few institutions, each of which only needs one reception system, in order to then forward the program to a large number of television sets (e.g. via a local cable network). Therefore, the additional effort for such professional solutions has so far been justifiable.
  • the invention has for its object to provide a tunable resonant circuit of the type mentioned, which enables a largely linear tuning characteristic with simple and inexpensive circuit means.
  • a first inductor is arranged in parallel with the two tuning diodes and is connected to ground via a capacitance, and in that a second parallel inductor is provided at the end of the first inductor facing away from the ground, the base of which is capacitively connected to ground and with an adjustable bias voltage is acted upon.
  • the resonant circuit according to the invention requires only surprisingly few inexpensive components, and it has been possible in practical tests to prove that a linear tuning characteristic and error-free demodulation can nevertheless be achieved and that the specified standards can be easily complied with. Because of the comparatively low overall costs, the invention enables economical series production for the first time.
  • the first parallel inductance which is connected to ground via a capacitance, assumes, among other things, the function of an elongation coil known per se at low frequency ranges, and moreover the first inductance galvanically connects the two electrodes of the tuning diodes facing away from the center point .
  • the second inductor which is likewise arranged in parallel, essentially determines the frequency of the resonance circuit, this inductor — like the first inductor — in an expedient embodiment of the invention being designed as an air coil.
  • the inductance values can thus be changed in order to "adjust" or linearize the tuning characteristic.
  • the value of the capacity mentioned can also be changed.
  • the demodulator also comprises an active element so that the resonant circuit can oscillate, and according to an expedient embodiment of the invention, the active element required for this is part of an integrated circuit known per se, which is mass-produced and thus inexpensively manufactured. Such an integrated circuit has so far not been used at the high frequencies in question here.
  • the signals emitted by a satellite, not shown, are received by a parabolic antenna 10 to which a converter 12 is connected.
  • the reception frequency here is 12 GHz, which is converted into a first intermediate frequency of 950-1750 MHz by means of the converter 12.
  • a further frequency conversion to a second intermediate frequency of 480 MHz takes place in a channel selector 14.
  • a demodulator 16 connects to the channel selector 14, and from here the demodulated signals arrive at a video processing circuit 18.
  • signals are available at an interface 20 in order to feed a television set 22.
  • the interface 20 can also be fed into a cable network (not shown) in order to supply a large number of television sets.
  • the second intermediate frequency passes from an amplifier 24 to a phase detector 26 which is followed by a further amplifier 28 and a frequency filter 30.
  • the demodulator 16 comprises a PLL control loop 32 which is provided by the frequency filter 30 leads to a feedback input 34 of a voltage controlled oscillator (VCO) 36.
  • VCO voltage controlled oscillator
  • the oscillator circuit 36 comprises a tunable resonant circuit, the structure of which is shown in FIG. 3.
  • a control signal is present at the above-mentioned feedback input 34, which reaches a center point 60 via a decoupling inductor 38, which connects the anodes of the two tuning diodes 40 and 42 to one another.
  • a first inductance 44 is arranged parallel to the tuning diodes 40, 42 and is connected to ground via a capacitance 46. Furthermore, a second inductor 48 is provided, at the base 54 of which there is a positive bias voltage U v . In addition, the base point 54 is connected to ground via a relatively small capacitance 50 and a relatively large capacitance 52 connected in parallel therewith.
  • Reference numbers 3 and 4 denote the numbered connections of an integrated circuit of the type TUA 2000, which have the required active element for includes the resonance circuit. As can be seen, the upper ends of the first inductor 44 and the second inductor 48 are each connected to said integrated circuit via capacitors 56 and 58.
  • the tuning characteristic curve 62 is largely linear in a range of 30 MHz.
  • a differential voltage U D is plotted on the lower horizontal axis in FIG. 4, which defines and sets the working range of the two tuning diodes 40 and 42 as the difference between the positive bias voltage U v already mentioned and the voltage at the center point 60.
  • the working range can thus be influenced by appropriate selection of the positive bias voltage U at the base point of the second inductance 48, in order to achieve an area with a constant tuning steepness in FIG. 4.
  • the anodes are of the two tuning diodes 40 and 42 are connected to one another via the center point 60, and a positive bias voltage U v is provided.
  • tuning diodes in reverse polarity can also be provided (here the cathodes are connected to one another via the center point 60), and it is then necessary to select the bias voltage U v negative (based on the center point 60).
  • the two capacitors 50 and 52 short-circuit the base point 54 of the second inductor 48 in terms of radio frequency. So that this short circuit is also effective in wide frequency ranges (e.g. also for video frequencies), one capacitance 50 has a relatively low value and the other parallel capacitance 52 has a relatively large value.
  • the inductors 38, 44 and 48 used are adjustable inductors and are designed as air coils.
  • the inductance values can be changed in a simple manner by spreading or pressing down individual windings of the air coil.
  • the tuning characteristic curve 62 can be brought into a desired position in relation to the center frequency of the resonance circuit.
  • the slope of the tuning characteristic curve 62 can be determined by Ver Changes in the values of the inductance 44 are effected.
  • a further linearization of the tuning characteristic curve 62 can be achieved by the decoupling inductance 38 known per se or by changes in the inductance value.
  • the bias voltage required for setting the working range of the two tuning diodes 40 and 42 can, moreover, expediently be found in the channel selector 14, so that a separate voltage source is not required.
  • the invention enables an inexpensive design of the amplifier 28, since an expensive operational amplifier with a high cut-off frequency (with the need for an additional negative supply voltage) can be dispensed with.
  • Another advantage of the invention is the possibility of using the already mentioned integrated circuit TUA 2000, the active element of which is used for the voltage-controlled oscillator 36. It is a well-known consumer IC that was previously used in the VHF tuner and has a new application in the invention, because this IC has not been used in connection with a PLL control loop. The use of the known IC contributes significantly to other features of the invention that the novel resonant circuit inexpensive in one Series production can be made.

Landscapes

  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Superheterodyne Receivers (AREA)
  • Stabilization Of Oscillater, Synchronisation, Frequency Synthesizers (AREA)
  • Inductance-Capacitance Distribution Constants And Capacitance-Resistance Oscillators (AREA)
  • Channel Selection Circuits, Automatic Tuning Circuits (AREA)
  • Circuits Of Receivers In General (AREA)
EP85106766A 1984-08-14 1985-06-01 Circuit résonateur accordable pour un démodulateur FM à boucle d'asservissement de phase Withdrawn EP0171529A3 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE19843429868 DE3429868A1 (de) 1984-08-14 1984-08-14 Abstimmbarer resonanzkreis fuer eine pll-fm - demodulator
DE3429868 1984-08-14

Publications (2)

Publication Number Publication Date
EP0171529A2 true EP0171529A2 (fr) 1986-02-19
EP0171529A3 EP0171529A3 (fr) 1988-03-30

Family

ID=6243008

Family Applications (1)

Application Number Title Priority Date Filing Date
EP85106766A Withdrawn EP0171529A3 (fr) 1984-08-14 1985-06-01 Circuit résonateur accordable pour un démodulateur FM à boucle d'asservissement de phase

Country Status (3)

Country Link
EP (1) EP0171529A3 (fr)
JP (1) JPS6149505A (fr)
DE (1) DE3429868A1 (fr)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2241846A (en) * 1990-03-10 1991-09-11 Marconi Gec Ltd Variable phase shift circuit
GB2274034A (en) * 1992-12-25 1994-07-06 Murata Manufacturing Co Voltage controlled oscillator

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS63176011A (ja) * 1987-01-16 1988-07-20 Clarion Co Ltd 同調電圧発生回路
JP6421435B2 (ja) * 2014-04-10 2018-11-14 株式会社デンソー 内燃機関の制御装置
JP6349895B2 (ja) * 2014-04-10 2018-07-04 株式会社デンソー 内燃機関用点火装置

Family Cites Families (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE1282104B (de) * 1965-07-27 1968-11-07 Siemens Ag In der Frequenz modulierbarer freischwingender Oszillator
US4450416A (en) * 1981-08-17 1984-05-22 General Electric Company Voltage controlled oscillator
FR2545667B1 (fr) * 1983-05-06 1985-07-12 Portenseigne Boucle a verrouillage de phase et dispositif de demodulation de signaux modules en frequence comprenant une telle boucle

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2241846A (en) * 1990-03-10 1991-09-11 Marconi Gec Ltd Variable phase shift circuit
GB2241846B (en) * 1990-03-10 1994-06-01 Marconi Gec Ltd Surface acoustic wave (saw) oscillator
GB2274034A (en) * 1992-12-25 1994-07-06 Murata Manufacturing Co Voltage controlled oscillator
US5534825A (en) * 1992-12-25 1996-07-09 Murata Manufacturing Co., Ltd. Volage-controlled oscillation circuit with an impedance element for carrier-to-noise compensation
GB2274034B (en) * 1992-12-25 1997-02-12 Murata Manufacturing Co Voltage-controller oscillation circuit

Also Published As

Publication number Publication date
JPS6149505A (ja) 1986-03-11
EP0171529A3 (fr) 1988-03-30
DE3429868A1 (de) 1986-02-20

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Inventor name: OHLER, MICHAEL, DIPL.-ING.